Comment on “Microyield and fracture in Polycrystalline MgO”

Baró, G.B.; Hornbogen, Erhard; Tangri, K.; Sinha, Mekhola; Lloyd, D. J.

doi:10.1007/bf00632775

Cited by 2 publications

(5 citation statements)

References 2 publications

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“…99 For MgO dislocation motion has been set into context with fracture toughness in the 1960s as well. 81,[100][101][102][103][104] While in single crystals emission of dislocation from the crack tip (at lower velocities) has been observed in MgO (and NaCl) [105][106][107][108][109][110][111][112][113][114][115][116][117] including a functional plastic zone, 117 interaction with grain boundaries was found to cause partially detrimental microcracking in polycrystalline MgO. 81,[100][101][102][103][104] Interestingly, the idea of dislocations being related to fracture toughness of ceramics was not much regarded in the wave of studies on improving fracture toughness of ceramics in the 1980s and 90s.…”

Section: Overview Of Developmentsmentioning

confidence: 99%

“…81,[100][101][102][103][104] While in single crystals emission of dislocation from the crack tip (at lower velocities) has been observed in MgO (and NaCl) [105][106][107][108][109][110][111][112][113][114][115][116][117] including a functional plastic zone, 117 interaction with grain boundaries was found to cause partially detrimental microcracking in polycrystalline MgO. 81,[100][101][102][103][104] Interestingly, the idea of dislocations being related to fracture toughness of ceramics was not much regarded in the wave of studies on improving fracture toughness of ceramics in the 1980s and 90s. 73,118 The limited number of slip systems and their incompatibility 119 may be a reason to discard dislocations for polycrystals, but, for example, Skrotzki et al suggested to evade incompatibility issues by texturing shown for KCl.…”

Section: Overview Of Developmentsmentioning

confidence: 99%

“…The formed shear bands then lead to nucleation of cracks at the grain boundary, limiting the impact of the plastic zone and leading to microcracking. 81,199,[100][101][102][103][104] Therefore, low or intermediate amounts of dislocations in polycrystals cannot substantially improve the mechanical behavior. 98 Dislocation motion around crack tips can shield the crack tip and enhance fracture toughness by forming a plastic zone.…”

Section: Limitation By the Necessity Of Nucleationmentioning

confidence: 99%

“…Deformation of polycrystalline ceramics at room temperature has also been investigated on LiF 98 and MgO 99 . For MgO dislocation motion has been set into context with fracture toughness in the 1960s as well 81,100–104 . While in single crystals emission of dislocation from the crack tip (at lower velocities) has been observed in MgO (and NaCl) 105–117 including a functional plastic zone, 117 interaction with grain boundaries was found to cause partially detrimental microcracking in polycrystalline MgO 81,100–104 …”

Section: Introductionmentioning

confidence: 99%

“…While a plastic zone was observed to form in MgO polycrystals, plasticity was limited to individual grains because grain boundaries impeded the transmission of dislocations. The formed shear bands then lead to nucleation of cracks at the grain boundary, limiting the impact of the plastic zone and leading to microcracking 81,199,100–104 . Therefore, low or intermediate amounts of dislocations in polycrystals cannot substantially improve the mechanical behavior 98 …”

Section: Introductionmentioning

confidence: 99%

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60 years of dislocations in ceramics: A conceptual framework for dislocation mechanics in ceramics

Porz

2022

Int J Ceramic Engine & Sci

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High‐tech ceramics are typically engineered by controlling point defects and interfaces while one‐dimensional dislocations have found much less attention so far. Nevertheless, their impact on almost any functional property and the sudden ease to fabricate them with novel synthesis methods, such as rapid densification, brings spotlight attention to dislocations as design dimension. Although the typical brittleness of ceramics insinuates the irrelevance of dislocations for mechanical behavior, abundant literature is spread over materials, decades, and disciplines, however, often unconnected. Here, a conceptual framework for dislocation mechanics in ceramics separated into five logical aspects, (1) fundamental mobility, (2) obstacles to motion, (3) limitation by necessity of nucleation, (4) motion complexity, and (5) avoidance of competing mechanisms, brings oversight into the complex behavior. In consequence, quicker identification of the limiting step allows to estimate the potential involved more precisely and to identify open research questions with greater ease. An introduction to dislocations and the functionality involved, a look back over the last six decades, and highlights of open question are dedicated to provide a framework and bridge the gap between the attached research fields.

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